Hyperthermia alone or in combination with x-irradiation may enhance tumor control. Before it can be applied clinically to enhance radiotherapy, substantial information will be needed concerning the response of both tumor and normal tissues. Among the potential techniques for producing controlled hyperthermia, ultrasound appears to offer adequate tissue penetration and can be focused on the tumor. The objectives of this project are: (1) To determine whether adjuvant ultrasound treatment can reduce the x-ray dose required to locally control a radiosensitive and a radioresistant tumor, (2) To study the effects of ultrasound treatment on the radiation tolerance of normal tissues (kidney, spinal cord, and bone). Ultrasonic enhancement of the tum r radiotherapy will be measured as the reduction in the TCD50, the radiation dose required to locally control 50 percent of the tumors. Normal tissue studies will be carried out as follows: (1) The enhancement of radiation damage to the kidneys will be determined by measuring the accumulation of radiopharmaceuticals. Rb-86 chloride and I-131 orthoridohippurate, which measure renal blood flow and function respectively. (2) The L2-L4 regions of the spinal cords of rats will be either treated with x-ray or combined x-ray and ultrasound. Reduced tolerance (with ultrasound) will be determined by comparing the radiation doses required to induce myelitis in 50 percent of each group. (3) Growing rats will have one hind limb treated with either x-ray or x-ray and ultrasound. Limb growth will be compared 60 days after treatment. The importance of the sequence of application of hyperthermia and x-ray is not completely known. To this end, we plan to study ultrasonic enhancement of x-ray effects on tumors and normal tissues by treating with ultrasound either immediately before or after x-irradiation.